Blood Transfusion Guidelines Updated by AABB

Marcia Frellick

October 12, 2016

New clinical practice guidelines from the AABB (formerly known as the American Association of Blood Banks) say that in most hemodynamically stable hospitalized adults, transfused red blood cells (RBCs) can be withheld until lower thresholds than previously recommended. In addition, RBCs can safely be given throughout their licensed dating period.

The expert panel, led by Jeffrey L. Carson, MD, from Rutgers Robert Wood Johnson Medical School, New Brunswick, New Jersey, published the guidelines online October 12 in JAMA. The AABB has long set standards for blood banking and transfusion practices.

The recommendation assigns two tiers of hemoglobin level transfusion triggers: 7 g/dL for hemodynamically stable adults, even those in critical care, and 8 g/dL for patients with preexisting cardiovascular disease or those undergoing cardiac or orthopedic surgery. The current hemoglobin threshold was 10 g/dL.

"Transfusion is a common therapeutic intervention for which there is considerable variation in clinical practice," the authors write. "If clinicians continue to adopt a restrictive transfusion strategy of 7 g/dL to 8 g/dL, the number of RBC transfusions would continue to decrease."

They add, "[S]tandard practice should be to initiate a transfusion with 1 unit of blood rather than 2 units. This would have potentially important implications for the use of blood transfusions and minimize the risks of infectious and noninfectious complications," the authors write.

The panel analyzed the results of 31 randomized trials that included 12,587 participants. They compared restrictive thresholds, where transfusion is not advised until the hemoglobin level is 7 to 8 g/dL, with liberal thresholds, under which transfusion is indicated at 9 to 10 g/dL.

They found that restrictive thresholds across trials were not associated with higher rates of poor outcomes, "including 30-day mortality, myocardial infarction, cerebrovascular accident, rebleeding, pneumonia, or thromboembolism."

The evidence is not strong enough to make any recommendation for patients with acute coronary syndrome, severe thrombocytopenia, and chronic transfusion-dependent anemia.

In an accompanying editorial, Mark H. Yazer, MD, and Darrell J. Triulzi, MD, from the Division of Transfusion Medicine, Department of Pathology, University of Pittsburgh Medical Center, Pennsylvania, write that the two-tiered approach to thresholds allows for more individualized transfusion decisions.

They note that for patients such as those having hip replacements, functional recovery has traditionally represented the primary rationale for transfusion, which can be achieved using either a conservative or liberal hemoglobin concentration transfusion trigger strategy.

The decision to transfuse should not be based only on the patient's hemoglobin level, and should include other factors including availability of alternative therapies and patient preferences, the editorialists write.

"That does not mean that guidelines...are without value, but rather that guidelines reflect general recommendations that apply to most patients in most situations. A major limitation of these guidelines is that they are based on hemoglobin level as the transfusion trigger," they explain. "Hemoglobin is a measure of the oxygen carrying capacity of blood, but does not indicate tissue oxygen delivery or the level of tissue oxygenation. Perhaps direct measurement of tissue oxygenation using noninvasive methods or plasma markers, such as base deficit, lactate, or other biomarkers, coupled with the measurement of hemoglobin level will provide a more clinically relevant indication of the need for RBC transfusion."

RBCs Safe Throughout Licensed Dating Period

The guidelines also indicate that transfusing RBCs stored for any length of time within their licensed dating period is as safe as transfusing blood that has been stored 10 days or less for most stable hospitalized patients, even neonates.

The finding is important, as 100 million units of blood are donated each year, but the optimal range of storage had not been determined.

For RBC storage, Dr Carson's team analyzed 13 randomized controlled trials that included 5515 participants randomly allocated to receive fresher blood or standard issue blood. They determined fresher blood did not improve clinical outcomes, which essentially affirms how many blood banks allocate blood in practice. Average duration of RBC storage in the United States is 17.9 days, the authors note.

The editorialists conclude, "These new guidelines from the AABB represent medicine at its best in that they are evidence based, derived from RCTs, reflect important clinical perspectives, and are definitive for conditions in which data are substantial, but provide greater flexibility for conditions in which data are less certain."

The guidelines were updated from 2012 guidelines, which were based on fewer, smaller trials and included a high risk for bias, according to the researchers.

"During the past 4 years," the authors write, "the number of patients enrolled in RBC transfusion [randomized controlled trials] has more than doubled, and many studies have incorporated methods to minimize the risk of bias and enrolled populations of patients receiving frequent blood transfusions."

Support for guideline development was provided by the AABB. Study coauthors report receiving support, personal fees, or stock options from Fresenius Kabi, Fenwal (a Fresenius Kabi company), Ortho Clinical Diagnostics, Octapharma, MacoPharm US, Castle Medical Inc, CSL Plasma Inc, Transfusion and Transplantation Technologies Inc, Cambium Medical Technologies, Biomet, CSL Behring, Masimo Corporation, Merck, AMAG Pharmaceuticals, Gauss Surgical, Vifor Pharma, and HbO2 Therapeutics. Dr Triulzi reported receiving grants from the National Heart, Lung, and Blood Institute and receiving personal fees for serving on an advisory board for Fresenius Kabi.

JAMA. Published online October 12, 2016. Guidelines full text, Editorial full text

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